Such closure elements, which are also called expanders, can be used, for example, for closing off, such as to seal, bores in engine or valve blocks or also chemical containers. High pressures of up to 1,000 bar prevail in the inside of a motor or valve block, and this is why stringent demands are made of the production quality and the material properties of the closure element for closing off, such as to seal, bores in such engine or valve blocks.
A closure element for closing off, such as to seal, bores subjected to internal pressure is known from WO 2009/000317 A1. This closure element has a cylindrical main body provided for insertion into the bore to be closed off, said main body having an outwardly projecting supporting flange. Disposed within the cylindrical main body is an expanding body which on the one hand forms a cover for the bore and on the other hand presses the main body inserted into the bore against the inner surface of the bore in the radial direction. In the still uninstalled state the expanding body is connected to the main body by a predetermined breaking point. For sealed closing off of the bore the cylindrical main body is first of all positioned in the bore with the expanding body fastened to it by the predetermined breaking point and then the expanding body is pressed into the main body by applying pressure such as to shear off the predetermined breaking point so that the expanding body exerts a radial pressure on the inside wall of the main body and thus expands the latter and presses it, forming a seal, against the wall of the bore to be closed off.